Where The Wild Things Were: Re-wilding and the Sixth Extinction - Biodiversity Conservation and Environmental Change - page 38

MANY LARGE
HERBIVORES

Wetter
Climate

High
evapotranspiration,
dry soils

Faeces and
Urine

PRODUCTIVE STEPPE
VEGETATION

Trampling and
Disturbance

Loss of
Herbivores

Diverse, productive,
grassy vegetation

Soils with high nutrient
content and fast
nutrient cycling

FEW
HERBIVORES

Add
Herbivores
(Re-wilding)

Water-logged soils

UNPRODUCTIVE
TUNDRA

Little disturbance,
slow nutrient cycling

Drier
Climate

Low
evapotranspiration

Slow plant growth

Figure 3.3 Alternate stable states of productive steppe vegetation, maintained by herbivory, and unpro-
ductive tundra, created when herbivores are lost. Climatic changes could also contribute to this mech-
anism; productive steppe vegetation is favoured in drier climates with less snow cover that facilitates
winter grazing (Chapin et al. 2004, Zimov et al. 2012).

A further consequence of this transformation is still unfolding. Without the action of thou-
sands of herbivore hooves and mouths, tundra soils remain insulated by snow in the winter,
which helps them to warm more rapidly in the summer. This facilitates summer thawing of
permafrost, potentially releasing vast quantities of carbon to the atmosphere and contribut-
ing to global warming (Zimov et al. 2006). Observations confirm that where herbivores are
removed, soils becomes waterlogged and unstable, leading them to gradually slide down-
slope into river systems, and leaving permafrost exposed to sun. Zimov argues that restor-
ation of the mammoth steppe vegetation and its inhabitants could help to avert an ecological
and climatic disaster (Zimov et al. 2006).
The plan for a Pleistocene park in Siberia seems feasible because there is experimental evi-
dence that vegetation change is reversible, and there is a range of extant species that can be
reintroduced from relatively nearby, which are valid conservation targets themselves. There
is also a high risk that inaction will have detrimental consequences. Furthermore, Siberia is
still home to an effective top carnivore—the tiger—one of the world's most endangered and
charismatic species. In this park, we find the key ingredients essential to a viable re-wilding
experiment; ecological justification and a flora that is viable in today's climate and into the
future, a suite of species that can fulfil the main herbivore feeding guilds, a top carnivore, and
space to accommodate it.